Touch activated membrane switches have become very common place for use in industrial equipment controls, home appliances and office equipment. The advantages membrane switches exhibit over mechanical electrical switches are numerous. For example, membrane switches are not prone to mechanical failure modes, such as breakage of moving parts, which are present in conventional mechanical switches. Furthermore, membrane switches present a more ergonomic human/machine interface and are also more aesthetically pleasing to the eye.
A typical membrane switch includes a lower membrane layer, an insulative spacer layer and an upper membrane layer. An upper face of the lower membrane layer is patterned with electrically conductive material to form at least a first electrode member and a second electrode member. Typically, the membrane switch includes an array of switches such that the electrically conductive material forms a plurality of pairs of first and second electrode members. Each pair of the first and second electrode members is used to complete separate conductive paths. The array of pairs is disposed in two dimensional array across the upper face of the lower membrane layer.
The insulative spacer layer is mounted to the upper face of the lower membrane layer. The spacer layer has an opening therethrough exposed over each pair of first and second electrode members. The upper membrane layer is mounted on the insulative spacer layer. A lower face of upper membrane layer has an electrically conductive shunt formed thereon over each of the opening of the spacer layer. Depression of the upper layer at each shunt completes an electrical circuit between the first electrode member and the second electrode member immediately below the selected shunt.
Typically, the lower layer is mounted on a substrate and a graphics layer is disposed on the upper membrane layer. The graphics layer includes indicia whereat depression of the graphics layer is to occur. The indicia are in alignment with the shunts on the upper membrane layer, and hence, the openings through the insulative spacial layer.
To make connection with to a device to be switched, the conductive material on the lower layer is extended to the periphery of such layer. The membrane switch as described above is then placed in a package. The package has external leads to connect to the various devices. The conductive material at the periphery of the lower layer is in electrical communication with the external leads by means of being connected internally within the switch package. The bonding of the conductive material to the leads of the package thus requires an additional fabrication step. It would be desirable to eliminate this fabrication step in which the external leads must be bonded to the conductive material.